diy masonry heater

Everyone on this planet should do whatever effort is possible, however small, to preserve our nature. I have decided to change my approach towards my heating habits. I have built a non polluting Finnish Fireplace and this how i did it.

Friday, February 24, 2006

Finnish Fireplace - Poele Finlandais

This is a masonry heater also called Finnish Fireplace. It is a very powerful heating device that could help you saving as much as 75% of your heating bill. It does so without polluting our atmosphere nor does it add any co2 to our breathing air. I have built it myself. Find out how?

Wednesday, February 22, 2006

diy masonry heater how to make the perfect fire

Let me tell you right away: i keep trying. You see the difficulty is to deal with what appears to be contradictory demands. One the one side you need a lot of air to reach high temperatures in the firebox ( to get a clean combustion ) and on the other side the less air comes through the firebox, the more heat is transferred to the walls. There it is: a balance between these 2 objectives.

The balance is difficult to obtain consistently because it varies according the dryness of the wood, type of wood, draft of the chimney.

First dryness: you should never burn wood with a humidity content of more than 25%, the ideal being between 20% and 15%. Get yourself a humidity tester, i have a testo 606 http://www.testo.com/. Even so i have noted that the slightest variation in humidity from one batch to the other impacts on air demand. One good advice, prepare your next firing as soon as possible. This will help the wood to get evenly dryer. Second, the denser the wood the harder it is to reach good internal temperatures. Therefore when using dense wood split it smaller than other woods. As a rule the denser your batch the more air you will need to get it going. Go ahead and open the ashdoor fully yes fully for a while. For light and drywood use less air especially if you have strong draft. I would leave the door ajar until you have real big flames all around yours logs. Then close the door with the vents open. When the flames start lowering, close your damper by half. When the flames start to change in pattern and they look more like lingering, close your damper further as well as all upper vents or injectors if applicable. Now your aim is to finnish your fire as soon as possible. Reduce the ashdoor air intake whenever possible but not so as to compromise the fire. Bear in mind that you want to terminate the fire as soon as possible and remember that it is at this stage that you are losing a lot of heat through the chimney. Finally at the ambers stage close the damper almost completely and close the ashdoor vents almost completely. If your firebox is real hot this stage should not last long. in my experience i get good results mixing hard and soft wood. That seems to give me the best of both worlds: good heat from soft wood helping the dense wood to release their gas, and good radiant heat from the embers of the hard wood. I told you it is a challenge

diy masonry heater how to make it work

I shall now adress what i find the most difficult part: how to make it work clean and efficient. First: if you have or plan to have a masonry heater; go ahead and buy yourself a good contact thermometer. I personnally use a Testo 925 http://www.testo.com/ fit with a contact probe. I am using it in two ways. Firstly, during the first month or so i would regularly monitor the temperatures within the firebox ( i drilled a small hole in the door frame for the probe ). With that i was able to see the difference in temperatures whith changing air intake. That is a good way to learn how much air you need at which stage of the fire. We will come to this later. Secondly, i take t° readings on 2 points of the surface of the heater which i have determined. One at the front and one at the side. I take these readings every mornings at 8.00. I note them on a spreadsheet together with useful informations ( outside t°, how many fires, etc...). That is also important because at the end of the day it is the surface temperature which radiates into the rooms. I know it all seems very silly but i can assure you that unless you have some sort of special bonds with the gods of fire, this is the only way to learn about your masonry heater and also about clean combustion. Next i shall deal with the fire itself and will try to share my modest experience.

diy masonry heater at work

Hello. I am back with a little bit of experience about using my masonry heater. We have had it running for nearly 2 months now. So far so good. No problems whatsoever. Believe me the thing is amazing. At first to get the walls dry and the house warm we lit one fire in the morning and another with one reload in the evening. In the morning i have measured average surface temperatures of 42°c. front /37°c sides. Now with my experience and a couple of minor improvments, we only lit one fire a day and temperatures are 44°c./39°c. In the evening before a new fire is lit the temperatures are still around 34°c/35°c, that is after nearly 24 hours. We found that this solution works well for us because it enables the central heating to kick on for 2x 1/2h per day. When we have 2 good fires/day i now have t° of 50°c et 41°c.I found that i had an excellent draft in my chimney so that some hot air was escaping from my home made rooftop damper. I have solved that and found significant improvment. I do recommend rooftop dampers. it enables us to keep our upstairs bedroom confortable. The chimney runs into one of them and we keep the door open.I am more and more positive about it. Next time i will adress what in my view is the most challenging part of a masonry heater: make a good fire...

Tuesday, February 21, 2006

diy masonry heater d24

There you are it is finished and working. I have plastered it with lime mortar. Note the heated bench covered with a granit stone ( the cat adores it ). Note also the stainless steel plate and cable to open the rooftop damper. The heater is now dry and i am monitoring the various effects on our heating bill and on our life. I shall keep you posted.

diy masonry heater d23

There you go: first firing. I was surprised to see that we had no problem whatsoever to get it started. To the right is my charming wife and to the left the heated bench. Some finishing left to be done .

diy masonry heater d19

The capping slab is on. It has been cast in a mould with Lafarge ciment fondu and artificial granulates. It was a heavy job ( 65kg )to carry it and put it in place. Note around it is ceramic fiber. The slab rests on the firebox on a thin layer of ceramic and comes right against the inner wall of the frame.

diy masonry heater d18

The photo is not very good and i apologise for this. Light problem i am afraid. I hope you can nevertheless see the firebox and the channels through it, the side smoke channels and the rear smoke channel. All i need to do now is to cast a capping slab that will sit on top of the firebox to seal it therefore forcing the smoke to go down the 3 channels.

diy masonry heater d17

Light work today i had other commitments to attend to. I nevertheless managed to plaster the outside of the inner frame. This is an important step with regards to security. This is to prevent any co leakage from the smoke channels to creep through the outer wall and to eventually finish in the room. The inside of the smoke channels was also plastered together with the outside of the firebox as i was building it. The mixture is the same i used for masonry ( clay/sand).

diy masonry heater d16

The cat is crossed, it is now to high for it to jump on! It did like sitting on top to get a good view over what we were doing. Well we will find a ladder. The frame is now at the same level than the throat. It will need to go another 4 bricks before we stop and put the capping slab.

diy masonry heater d14 & d15

I know what you guys are thinking: this guy is slow and sleeps on his work. That's the way my wife is currently thinking. Honey will it be ready for next summer you think? Very very funny. It does not look like it but it grows higher ( the masonry heater that is). Look at the cd rack next to it and you will see that it is now 1.40 meters high. At the end of this working day it has to be higher tha my wife otherwise she kills me.

I am ok. the thing is now taller than my wife. The firebox stands now at 1.75 meters. In fact the sides of the firebox will not go higher. Only the front will go another 4 courses and 2 columns at the back to allow smoke to go down the sides channels as well as down the back channel. I am mad at Bosch ( yes the tool company ). you remember i was telling you the hard time i had cutting those refractory bricks. I had tried it with with my Metabo diamond disk without succes, then i bought a Bosch PRO diamond disk. This was supposed to be the best of the best made among other uses for cutting refractory bricks. Mind you at 170€ it could well be... I used it on one brick then i stopped. it was useless. Luckily my dealer found another disk by a company called Inter Diamant. I bought it and i have to say it is fantastic. It goes through like in melted butter. The dealer kindly accepted to take the Bosch disk back and will settle this with Bosch.

diy masonry heater d13

This is an important stage in the building process: the setting of the throat. The photo is taken from above and one can see how the firebox is narrowed. That is the throat the purpose of which is twofold 1- to reflect the heat back to the fire to intensify heat and 2- to accelerate the gasflow therefore creating gas turbulences to be reignited. The throat has been casted with ciment fondu and alag granulates all from Lafarge.

diy masonry heater d12

Work is continuing albeit slowly. Considering the shape of the heater there is a lot of cutting to be done. I use a 230mm Metabo grinder http://www.metabo.com/ connected to a Festool vacuum cleaner http://www.festool.com/ . It works fine for the regular bricks. For the refractory it is a real pain. I have tried every trick in the book, diamond, regular even a metal disk. The best i have found is a regular stone disk. One disk every two cuts... I should have rented a wet saw.

diy masonry heater d11

The inner frame wall is being built. Note insulation at the back. I dont't want the heat to escape to my charming neighbours. The white stuff is not material for Santa Claus beard... It is ceramic fibre, the aim of which is to allow for expansion.

diy masonry heater d10

Firebox is being built using low duty refractory bricks and fondulite fireproof ciment from Lafarge. Note the 2 blacks castings, these are the secondary air injectors feeding air to the upper section of the fire.

diy masonry heater d9

The bottom is finished and ready to accomodate the firebox floor. Note the smoke channels on either sides of the firebox. From now on i will use refractory mortar for the firebox core, clay mortar for the inner frame and common lime/ciment mortar for the outer shell. Note also to the left the start of the heated bench.

diy masonry heater d6,7,8

The first 3 courses of bricks have been laid. Now you can clearly see the ashbox in the middle on top of which will rest the firebox. You can also note the smoke channels on either sides. The two channels will join to the left in a 1 meter long liner connecting with the existing chimney.

diy masonry heater d5

I am satisfied with the various castings. I have done them with ciment fondu and artificial granulates all from Lafarge http://www.cimentfondu.com/ . It is guaranteed up to 1100°c and they claim it can cope well with thermal shocks. On the picture from left to right, air injectors, firebox floor, lintel beam for the door and underneath is the throat.

diy masonry heater d4

Professor 2xH out of finland has sent me the drawings for the fireplace. Very complete i must say with lots of technical infos such as number of bricks, kg of mortar, total weight of the fireplace and total output of kilowats. With all infos i have been busy collecting the necessary materials ( on the photos the refractory bricks ). I am also buiding the moulds for the castable elements such as firebox floor, capping, throat etc... I hope i'll finish these today.

I have decided to do something at my modest scale to fight global warming. Heating in our societies is the main culprit for outdoor pollution. Having attended this summer a workshop in Czech Rep on bulding finnish contraflows masonry heaters, i have my mind set on building one at my brussels home. Having read numerous articles on the subject i am convinced that is the way to go. For those interested, i shall keep them abreast of various construction steps. Do not hesitate to drop a line. On the photo my living room. The masonry heater ( mh ) will be in the right hand corner whereas the existing chimney will be demolished.